Method for cutting a surgical suture tip

ABSTRACT

An apparatus and method for forming a cut end of a surgical suture tip. The apparatus including a first and second cutting dies with a channel for receiving a suture. Mechanical actuators are provided to moving the cutting dies from an open to a closed position. The cutting dies are adapted to trap and compressing the suture. A cutting blade is provided for cutting the surgical suture tip adjacent to the first and second cutting dies when the cutting dies are closed. 
     A second cutting die having a notch which is aligned to insert in said channel and secure a suture there between. A mechanical activator is provided to move said dies. A cutting blade is provided to cut the suture secured between said dies. A method for forming cut ends of a suture tip is also described.

FIELD OF THE INVENTION

The present invention is directed to systems for processing strings andyarns. More particularly, the present invention is directed to automatedsystems for thermally forming and cutting surgical sutures.

BACKGROUND OF THE INVENTION

Various automated systems for forming and cutting surgical suture tipsexist or are known in the art. In one such machine, means forsimultaneously advancing in parallel at least six separate strands ofsuture material, and six independent tensioners for maintainingrespective parallel portions of each of the six strands at a presettension are provided. Once a predetermined length of suture material hadbeen advanced by the advancing means, a horizontal heater bar(positioned perpendicular to the six suture strands) is actuated by anelectronically controlled solenoid which moves a planar heater bar intocontact with one side of the suture strands for a predetermined dwelltime. Once the predetermined dwell time has elapsed, the solenoidretracts the heater bar to its original position, and the heat exposed(or heat-stiffened) section of suture material is advanced to a cuttingstation. At the cutting station, the heat-stiffened section of suturematerial is cut at its midpoint, thereby producing a suture with twostiffened ends. Other mechanisms for forming and cutting surgical suturetips are shown in U.S. Pat. Nos. 4,832,025, 4,806,737 and 5,226,336 toCoates. The system described in the Coates patents uses convective ornon-contact heating to form suture tips.

Known systems for forming and cutting surgical suture tips suffer fromtwo primary drawbacks. First, such systems typically produce a suturetip which lacks a substantially uniform cross-section. Second, suchsystems typically cut the suture tip in an imprecise manner, therebyleaving a cut end which may be irregular or distorted in shape. From amanufacturing standpoint, suture tips having non-uniform cross-sectionsand/or irregular or distorted cut ends are undesirable because, amongother things, such sutures are difficult to insert into needles.

It is therefore an object of the present invention to provide a surgicalsuture having a tip with a substantially uniform cross-section and aprecisely cut end which may be easily inserted into a needle.

It is a further object of the present invention to an automated systemand method for manufacturing surgical sutures having tips withsubstantially uniform cross-sections.

It is a still further object of the present invention to provide anautomated system and method for making surgical sutures with tips havingprecisely cut ends.

These and other objects and advantages of the invention will become morefully apparent from the description and claims which follow or may belearned by the practice of the invention.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for forming a cut endof a surgical suture tip having a length and a cross-section that isperpendicular to the length. The apparatus includes a first cutting diehaving a first face with a channel therein for receiving at least aportion of the cross-section of the surgical suture tip, the channel isaligned along a common axis. A second cutting die having a second faceis also provided. At least one mechanical actuator is provided formoving the first face of the first cutting die against the second faceof the second cutting die and for contacting the channel in the firstcutting die against an outer surface of the cross-section of thesurgical suture tip. The channel in the first cutting die and the secondface define a singular cutting die opening when the first face of thefirst cutting die is positioned against the second face of the secondcutting die. The singular cutting die opening has a cross-sectionperpendicular to the common axis that is small enough to compress thecross-section of the surgical suture tip when the first face of thefirst cutting die is positioned against the second face of the secondcutting die. A cutting blade is provided for cutting the surgical suturetip when the first face of the first cutting die is positioned againstthe second face of the second cutting die.

In accordance with a still further aspect, the present invention isdirected to a method for forming a cut end of a surgical suture tiphaving a length and a cross-section that is perpendicular to the length.The length of the surgical suture tip is positioned between a channel ina first face of a first cutting die and a second face of a secondcutting die, the channel in the first cutting die being aligned along acommon axis. After the positioning step, a portion of the cross-sectionof the surgical suture tip is received into the channel in the firstcutting die, and the first and second faces of the first and secondcutting dies, respectively, are moved against each other. The channel inthe first cutting die and the second face define a singular cutting dieopening when the first face of the first cutting die is positionedagainst the second face of the second cutting die. The singular cuttingdie opening has a cross-section perpendicular to the common axis that issmall enough to compress the cross-section of the surgical suture tipwhen the first face of the first cutting die is positioned against thesecond face of the second cutting die. The cut end is formed by moving acutting blade across a point adjacent to the first and second cuttingdies when the cutting dies are in their closed position.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantagesand objects of the invention are obtained and can be appreciated, a moreparticular description of the invention briefly described above will berendered by reference to a specific embodiment thereof which isillustrated in the appended drawings. Understanding that these drawingsdepict only a typical embodiment of the invention and are not thereforeto be considered limiting of its scope, the invention and the presentlyunderstood best mode thereof will be described and explained withadditional specificity and detail through the use of the accompanyingdrawings.

FIG. 1 is a schematic diagram showing a machine for thermally formingand cutting surgical sutures, in accordance with a preferred embodimentof the present invention.

FIG. 2 is an isometric view of a suture tipping station formed from apair of opposing heating dies both of which are in their retractedpositions, in accordance with a preferred embodiment of the presentinvention.

FIG. 3 is an isometric view of the suture tipping station of FIG. 2,wherein one of the heating dies in the station is in its retractedposition and the other heating die in the station is in its extendedposition.

FIG. 4 is a further isometric view of the suture tipping station of FIG.2, wherein both of the heating dies in the station are in their extendedor closed positions.

FIGS. 5 and 6 show isometric views of the opposing heating diesillustrated in FIGS. 2-4.

FIG. 7 is a cross-sectional view of an exemplary length of surgicalsuture material which has not been contacted by the heating dies of theheating station shown in FIGS. 2-4.

FIG. 8 is a graph illustrating the statistical distribution of thevarying cross-sectional diameters found in the unfinished suturematerial depicted in FIG. 7.

FIG. 9 is a cross-sectional view of an exemplary length of a surgicalsuture tip which has been thermally formed by the heating dies of theheating station shown in FIGS. 2-4, in accordance with a preferredembodiment of the present invention.

FIG. 10 is a graph illustrating the statistical distribution of thegenerally uniform cross-sectional diameters found in the thermallyformed suture tip depicted in FIG. 9 and the statistical relationshipbetween these generally uniform tip diameters and the varyingcross-sectional diameters found in the body portion of a suture made inaccordance with a preferred embodiment of the present invention.

FIG. 11 is an isometric view of a suture cutting station formed from apair of opposing cutting dies, wherein one of the cutting dies is in itsretracted position and the other cutting die is in its extendedposition, in accordance with a preferred embodiment of the presentinvention.

FIG. 12 is an isometric view of the suture cutting station of FIG. 11,wherein both of the cutting dies in the station are in their closedpositions, in accordance with a preferred embodiment of the presentinvention.

FIG. 13 is an isometric view of the suture cutting station of FIG. 12,illustrating the position of the cutting dies in the station as acutting blade moves through a cross-section of thermally formed surgicalsuture material positioned in the cutting station, in accordance with apreferred embodiment of the present invention.

FIG. 14 is a cross-sectional view showing the components of the suturecutting station of FIGS. 11-13.

FIG. 15 is an exploded isometric view of the opposing cutting dies shownin FIGS. 12-13.

FIG. 16 is an exploded front elevational view of the opposing cuttingdies shown in FIG. 15.

FIG. 17 is a front elevational view of the opposing cutting dies ofFIGS. 15-16, in accordance with a preferred embodiment of the presentinvention.

FIG. 18 is a cross-sectional view of a suture cutting station forsimultaneously cutting a length of thermally formed surgical suturematerial at two different locations, in accordance with an alternativepreferred embodiment of the present invention.

FIG. 19 is a side view of the suture cutting station shown in FIG. 18.

FIG. 20 shows the position of optical sensors used for monitoring themovement of the heating and cutting dies in the combined heating andcutting station shown in FIGS. 2-4 and 11-13, in accordance with apreferred embodiment of the present invention.

FIG. 21 is a cross-sectional view of a moving clamp shown in its closedstate for grasping and advancing surgical suture material, in accordancewith a preferred embodiment of the present invention.

FIG. 22 is a cross-sectional view showing the moving clamp of FIG. 21 inits open state, in accordance with a preferred embodiment of the presentinvention.

FIG. 23 is a cross-sectional view of a stationary clamp shown in itsclosed state for grasping surgical suture material, in accordance with apreferred embodiment of the present invention.

FIG. 24 is a cross-sectional view showing the stationary clamp of FIG.23 in its open state, in accordance with a preferred embodiment of thepresent invention.

FIG. 25 is an isometric view of a system for tensioning a length ofsurgical suture material, in accordance with a preferred embodiment ofthe present invention.

FIG. 26 is an isometric view of an optical detection system fordetecting knots in surgical suture material passing through the system,in accordance with a preferred embodiment of the present invention.

FIG. 27 is a further isometric view showing a knot positioned betweenthe optical source and the optical detector of the knot detection systemof FIG. 26, in accordance with a preferred embodiment of the presentinvention.

FIG. 28 is a cross-sectional view of FIG. 27, showing a knot positionedbetween the optical source and the optical detector of the knotdetection system of FIG. 26, in accordance with a preferred embodimentof the present invention.

FIG. 29 is an isometric view of a suture material holding arm which isused for producing sutures having lengths that exceed the length of themachine of FIG. 1, in accordance with a preferred embodiment of thepresent invention.

FIG. 30 is a cross-sectional view showing the suture material holdingarm of FIG. 29 in its retracted position.

FIG. 31 is a cross-sectional view showing the suture material holdingarm of FIG. 29 in its extended position.

DETAILED DESCRIPTION OF THE INVENTION Overall System Operation

Referring now to FIG. 1, there is shown a schematic diagram showing amachine 10 for thermally forming and cutting surgical sutures, inaccordance with a preferred embodiment of the present invention. Acontinuous length of unfinished surgical suture material 110 is suppliedto machine 10 from a supply spool 100 having unfinished surgical suturematerial 110 wound thereon. Unfinished surgical suture material 110 fromsupply spool 100 is initially advanced through a tensioning assembly 200for creating a tension in the unfinished surgical suture material, andthen through a knot detector system 300 for detecting whether a knot ispresent in any unfinished surgical suture material 110 passing throughknot detector system 300. After passing through the knot detector system300, the unfinished surgical suture material is advanced to a combinedheating and cutting station 400, where (i) a predetermined length of theunfinished surgical suture material 110 is thermally formed into alength of surgical suture tip material, and (ii) the thermally formedsurgical suture tip material is cut, thereby yielding a finishedsurgical suture 120 having a body portion formed of unfinished surgicalsuture material 110 and a thermally formed tip portion terminating witha cut end.

As explained more fully below, the unfinished surgical suture material110 from supply spool 100 is advanced through machine 10 by a movingclamp 500 which is coupled to a linear actuator 550 for driving themoving clamp 500 between a starting or home position 510 on one side ofthe combined heating and cutting station 400 and an end position 512 onthe other side of combined heating and cutting station 400. Moving clamp500 has a grasping (or closed) state shown in FIG. 21, and anon-grasping (or open) state shown in FIG. 22. In accordance withinstructions received from a controller 800, the moving clamp 500selectively grasps and pulls the unfinished surgical suture material 110through machine 10 in order to facilitate the manufacture of thefinished surgical sutures 120. In addition to advancing unfinishedsurgical suture material through the machine, the moving clamp 500functions to initially position and align the unfinished surgical suturematerial 110 within combined heating and cutting station 400.

During operation of the machine 10, the moving clamp 500 initiallygrasps or closes on the unfinished surgical suture material 110 at thehome position 510. Next, while the moving clamp 500 remains in itsgrasping or closed state, the linear actuator 550 drives the movingclamp 500 from its home position 510 to the end position 512. As thelinear actuator 550 drives moving clamp 500 from its home position 510to its position 512, the moving clamp 500 pulls a length of theunfinished surgical suture material 110 through the combined heating andcutting station 400 and through a stationary clamp 600 positionedbetween the end position 512 and the combined heating and cuttingstation 400. Like the moving clamp 500, the stationary clamp 600 has agrasping (or closed) state which is shown in FIG. 23, and a non-grasping(or open) state shown in FIG. 24. As the linear actuator 550 drives themoving clamp 500 from home position 510 to end position 512, thestationary clamp 600 is in its open state. After the moving clampreaches its end position 512, the stationary clamp 600 grasps or closeson the unfinished surgical suture material 110 positioned within thestationary clamp 600. The position of stationary clamp 600 along thelength of machine 10 may be adjusted in order to facilitate the creationof sutures with different lengths.

As illustrated in FIG. 2, the combined heating and cutting station 400includes a pair of opposing heating dies 402, 404, and a pair ofopposing cutting dies 450, 452. The opposing heating dies 402, 404 haveboth an open and a closed state. Similarly, the opposing cutting dies450, 452 have an open and a closed state. When, as described above, thelinear actuator 550 drives the moving clamp 500 from home position 510to end position 512, both the opposing heating dies 402, 404 and theopposing cutting dies 450, 452 in the combined heating and cuttingstation 400 are in their open positions. After the moving clamp reachesits end position 512 and the stationary clamp 600 has grasped or closedon the unfinished surgical suture material 110 positioned within thestationary clamp 600, the heating dies 402, 404 move from their openstate to their closed state in order to thermally form a predeterminedlength of surgical suture tip material. The operation of the heatingdies 402, 404 is described in greater detail below in connection withFIGS. 2-10. After the heating dies 402, 404 move from their open totheir closed state, the moving clamp 500 releases the unfinishedsurgical suture material 110 in its grasp and, while the moving clamp isin its open or non-grasping state, the linear actuator 550 drives themoving clamp 500 from its end position 512 to its home position 510where the moving clamp closes on a next piece of unfinished surgicalsuture material 110.

After the opposing heating dies 402, 404 have been in their closed statefor a predetermined period of time, the heating dies 402, 404 move fromtheir closed to their open state, thereby exposing a predeterminedlength of surgical suture tip material positioned between the opposingheating dies 402, 404. Next, while the surgical suture tip materialremains positioned between the open heating dies 402, 404, the opposingcutting dies 450, 452 move from their open state to their closed statein order to "pinch" or firmly grasp the predetermined length of surgicalsuture tip material, preferably at a point adjacent to the midsection ofthe length of surgical suture tip material formed by the heating dies402, 404. While the cutting dies 450, 452 are in their closed position,a cutting blade 480 is moved across a cross-section of the surgicalsuture tip material at a point adjacent to the cutting dies 450, 452,thereby yielding a thermally formed surgical suture tip with a cut end.

Thereafter, the cutting dies 450, 452 move from their closed position totheir open position and the stationary clamp 600 releases the surgicalsuture material within its grasp. As the stationary clamp opens andreleases the previously grasped surgical suture material, a finishedsurgical suture 120 having a thermally formed and cut tip falls bygravity onto an arm affixed to the stationary clamp 600. Prior to thetime that the cutting dies 450, 452 are moved from their closed to theiropen position, the moving clamp 500 grasps or closes on the surgicalsuture material at home position 510, and the process described above isthen preferably repeated in order to manufacture further finishedsurgical sutures 120. Since the tensioning assembly 200 exerts atensioning force on the surgical suture material 110 positioned withinmachine 10, it is important for the moving clamp 500 to grasp or closeon the surgical suture material at home position 510 prior to the timethat the cutting dies 450, 452 are moved from their closed to their openposition, in order to prevent the tensioning assembly 200 from pullingthe trailing end of the surgical suture material cut by blade 480 in areverse direction past home position 510 when the cutting dies 450, 452are opened.

The unfinished surgical suture material 110 used in machine 10 formanufacturing the finished sutures 120 may consist of any thermoplasticbraided suture material such as, for example, a polyester braided suturematerial, or a polyamide or polyolyfin suture material. In a preferredembodiment of the present invention described more fully below, theunfinished surgical suture material 110 used in machine 10 is a braidedsuture material formed of a polyethylene terephthalate, such as thatsold by Ethicon, Inc. under the trademark ETHIBOND® EXCEL®. In apreferred embodiment, a Simatic model TI435 controller manufactured bySiemens is used to implement controller 800. An operator interface ispreferably coupled to the controller 800.

Operation of Heating Dies

As mentioned above, after the moving clamp 500 has reached its endposition 512 and the stationary clamp 600 has grasped or closed on theunfinished surgical suture material 110 positioned within the stationaryclamp 600, the heating dies 402, 404 in the combined heating and cuttingstation 400 operate to thermally form a predetermined length of surgicalsuture tip material from the unfinished surgical suture material 110positioned within the station 400. During the operation of the heatingdies 402, 404, the unfinished surgical suture material 110 is suspendedin an aligned and fixed positioned within station 400 by the stationaryclamp 600 which is positioned on one side of station 400, and by thepulley 514 which is positioned on an opposing side of station 400. Inaddition, during the operation of the heating dies 402, 404, theunfinished surgical suture material 110 suspended within station 400 ismaintained with a preset tension by tensioning system 200.

FIGS. 2-4 show three views of the combined heating and cutting station400. Each of the views illustrates the position of the heating dies 402,404 at a particular point during a suture tipping cycle. Referring nowspecifically to FIG. 2, there is shown an isometric view of station 400,wherein the heating dies 402, 404 are both in their retracted or openpositions. FIG. 2 shows the position of heating dies 402, 404 when themoving clamp 500 has reached its end position 512 and the stationaryclamp 600 grasps or closes on the unfinished surgical suture material110 positioned within the stationary clamp 600. After the moving clamp500 has reached its end position 512 and the stationary clamp 600 hasgrasped or closed on the unfinished surgical suture material 110positioned within the stationary clamp 600, a master cylinder 406(controlled by controller 800) drives the heating die 404 from itsretracted to its extended position. FIG. 3 shows the position of theheating dies 402, 404 after the master cylinder 406 has moved heatingdie 404 to its extended position. As the heating die 404 is moved to itsextended position, a cross-sectional portion of the suture material 110suspended within station 400 is received into a groove or channel 405(shown in FIG. 6) within heating die 404. A pair of V-shaped guides404a, 404b are affixed to the ends of the heating die 404 in order tofacilitate the guidance of the unfinished suture material 110 intogroove 405 during this step. In a preferred embodiment of the presentinvention, the master cylinder 406 causes the groove 405 in the heatingdie 404 to slightly overshoot (or pass) the centerline of the unfinishedsuture material 110 suspended within the station 400, in order to ensurethat at least a cross-sectional portion of the unfinished suturematerial 110 is in fact received into the groove 405.

After the master cylinder 406 has moved heating die 404 to its extendedposition, a slave cylinder 408 (controlled by controller 800) drivesheating die 402 from its retracted to its extended position. FIG. 4shows the position of the heating dies 402, 404 after the slave cylinder408 has moved heating die 402 to its extended position. As the heatingdie 402 is moved to its extended position, the cross-sectional portionof the suture material 110 which was not previously received into groove405 is received into a groove or channel 403 (shown in FIG. 5) withinheating die 402. After the slave cylinder 408 has driven heating die 402to its extended position, the face 405a of heating die 404 standsadjacent to and abuts the face 403a of heating die 402. In a preferredembodiment of the present invention, the force used by slave cylinder408 to drive heating die 402 to its extended position is less than theforce used by master cylinder 406 to drive heating die 404 to itsextended position. The use of a reduced force by the slave cylinder 406insures that the position of the heating die 404 will not be disturbedwhen the heating die 402 is brought into contact with the heating die404 as shown in FIG. 4. After faces 403a and 405a have been broughttogether and the heating dies 402, 404 have "closed on" the unfinishedsurgical suture material 110 as shown in FIG. 4, the heating dies 402,404 remain in their closed or extended positions for a predetermineddwell time. Thereafter, the cylinders 406 and 408 open the heating dies402, 404 by bringing them back to their initial retracted positions,thereby exposing a predetermined length of thermally formed surgicalsuture tip material suspended between opposing open heating dies 402,404.

In the preferred embodiment of the present invention, the cross-sectionsof grooves 403 and 405 each represent a half circle or semi-circle suchthat, when faces 403a and 405a are brought into contact with each otheras shown in FIG. 4, grooves 403 and 405 together form a singularcylindrical opening with a circular cross section (hereinafter "theheating die cross-section") running perpendicular to the axis of thecylindrical opening. The axis of the cylindrical opening formed bygrooves 403 and 405 is aligned in parallel with the length of thesurgical suture material 110 along the "x" axis (shown in FIGS. 2-4). Inthe preferred embodiment of the present invention, the diameter of theheating die cross-section is always less than the averagecross-sectional size of the unfinished surgical suture material 110provided from supply spool 100. By making the diameter of the heatingdie cross-section less than the average cross-sectional size of theunfinished surgical suture material 110, the present invention insuresthat grooves 403 and 405 both contact and apply pressure to the suturematerial 110 during the suture tipping process. The tension maintainedin the unfinished surgical suture material 110 by tensioning assembly200 functions to prevent the heating die cross-section from overlypinching or constricting the suture material during the suture tippingprocess.

Referring now to FIG. 7, there is shown a cross-sectional view of anexemplary length of unfinished surgical suture material 110 which hasnot been contacted by the heating dies 402, 404 of station 400.Unfinished suture material 110 (as shown in FIG. 7) is used to form theuntipped body portions of sutures made in accordance with the presentinvention. Unfinished suture material 110 is formed of a plurality ofyarns 112, each of which is formed from several strands or filaments114. Since unfinished suture material 110 is braided, its cross-sectionis not uniformly circular. On the contrary, the diameter of thecross-section of the unfinished suture material 110 varies depending onthe position of the diameter measured. Thus, the three exemplarydiameter measurements 117, 118, 119 of the suture material 110 shown inFIG. 7, all of which pass through the centroid 116 of the cross-section,each have a different length. FIG. 8 shows a graph illustrating thestatistical distribution of the varying cross-sectional diameters foundin the unfinished suture material depicted in FIG. 7, and, inparticular, the varying cross-sectional diameters found in unfinishedsize 0 ETHIBOND EXCEL surgical suture material. As shown in FIG. 8, fora given length of unfinished surgical suture material 110, there is anaverage cross-sectional diameter (D_(avg)), a first standard deviationcross-sectional diameter (D_(sd1)) representing a cross-sectionaldiameter length that is one standard deviation below D_(avg), and asecond standard deviation cross-sectional diameter (D_(sd2))representing a cross-sectional diameter length that is two standarddeviations below D_(avg).

In a first preferred embodiment of the present invention, the diameterof the heating die cross-section formed by grooves 403 and 405 is aconstant that is less than the D_(avg) value for the unfinished suturematerial 110; in a second preferred embodiment of the present invention,the diameter of the heating die cross-section formed by grooves 403 and405 is a constant that is about equal to the D_(sd1) value for theunfinished suture material 110; and in a still further preferredembodiment of the present invention, the diameter of the heating diecross-section formed by grooves 403 and 405 is a constant that is aboutequal to the D_(sd2) value for the unfinished suture material 110.

Referring now to FIG. 9, there is shown a cross-section 122 of anexemplary length of a surgical suture tip that has been thermally formedby the heating dies 402, 404 of station 400 as described above inconnection with FIGS. 2-4. The exemplary cross-section 122 shown in FIG.9 was thermally formed (or finished) using a heating die cross-sectionhaving a constant diameter that was about equal to the D_(sd2) value forthe unfinished suture material 110 initially supplied to station 400. Asa result of the fact that the diameter of the heating die cross-sectionwas less than the D_(avg) value for the unfinished suture material 110,the unfinished suture material 110 was contacted by the heating dies402, 404 during the thermal heat tipping process. The contacting of theheating dies 402, 404 with the unfinished suture material 110 during thethermal heat tipping process, together with the fact that the suturematerial 110 is under tension during this process, causes the suturematerial 110 which is contacted by the heating dies 402, 404 to becompressed, thereby resulting in the "rounding" of filaments (such asfilaments 124) positioned about the perimeter of cross-section 122. As aresult of this "rounding" of the filaments about its perimeter, thecross-section 122 is generally uniform in diameter. In contrast to thevarying diameters of the cross-section of the unfinished suture material110 shown in FIG. 7, the diameters of the cross-section 122 aregenerally constant irrespective of the position of the diametermeasured. Thus, the three exemplary diameter measurements 126, 127, 128of the cross-section 122 shown in FIG. 9, all of which pass through thecentroid 129 of the cross-section, each have about the same length.Tables I, II, and III illustrate the cross-sectional diameters of size0, 2/0 and 3/0 sutures having body portions formed from unfinishedETHIBOND® EXCEL® suture material and tip portions which have been formedby dies 402,404 (having a constant cross-sectional diameter about equalto the D_(sd2) value of the unfinished suture material), in accordancewith the present invention. As these tables show, the present inventionresults in sutures having tip portions (110a) with a cross-section thatis both smaller in diameter and more uniform (i.e., smaller diameterstandard deviation) than the unfinished suture body portions (110b)adjacent to such tip portions.

                  TABLE I                                                         ______________________________________                                        Size Measurements of Tip and Body Diameters of Size 0 Sutures                          SET 1            SET 2                                               BODY/TIP END                                                                             TIP END  BODY      TIP END                                                                              BODY                                     DIAMETER   MILS     MILS      MILS   MILS                                     ______________________________________                                        SAMPLE #                                                                      1          17.44    18.97     17.92  20.85                                    2          17.64    20.40     17.82  19.41                                    3          17.29    18.45     18.10  20.08                                    4          17.52    18.96     17.70  19.56                                    5          17.59    19.38     17.63  19.43                                    6          17.82    19.47     17.82  20.70                                    7          17.90    19.74     17.45  18.57                                    8          17.57    20.47     18.20  19.31                                    9          17.43    20.44     17.70  19.83                                    10         17.61    20.07     17.90  19.27                                    AVERAGE    17.58    19.63     17.82  19.70                                    STANDARD DEV.                                                                             0.18     0.71      0.22   0.69                                    ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        Size Measurements of Tip and Body Diameters of Size 2/0 Sutures                        SET 1            SET 2                                               BODY/TIP END                                                                             TIP END  BODY      TIP END                                                                              BODY                                     DIAMETER   MILS     MILS      MILS   MILS                                     ______________________________________                                        SAMPLE #                                                                      1          14.78    16.66     15.39  17.70                                    2          14.98    17.74     14.55  15.93                                    3          15.03    16.84     14.87  15.87                                    4          15.04    17.44     14.92  16.91                                    5          15.14    16.54     14.74  17.15                                    6          15.19    16.71     14.61  16.07                                    7          14.97    17.05     15.24  20.01                                    8          14.86    15.41     14.75  17.53                                    9          15.04    17.17     14.61  16.39                                    10         14.89    18.57     14.85  17.12                                    AVERAGE    14.99    17.01     14.85  17.07                                    STANDARD DEV.                                                                             0.12     0.83      0.27   1.22                                    ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Size Measurements of Tip and Body Diameters of Size 3/0 Sutures                        SET 1            SET 2                                               BODY/TIP END                                                                             TIP END  BODY      TIP END                                                                              BODY                                     DIAMETER   MILS     MILS      MILS   MILS                                     ______________________________________                                        SAMPLE #                                                                      1          11.87    15.27     11.73  13.31                                    2          11.84    13.82     12.00  12.98                                    3          11.66    14.05     11.80  13.47                                    4          11.89    15.40     11.64  13.37                                    5          11.63    15.93     11.65  13.08                                    6          11.55    15.01     11.68  13.53                                    7          11.56    14.60     11.37  12.82                                    8          11.77    14.98     11.45  13.79                                    9          11.66    13.85     11.66  13.39                                    10         11.66    13.89     11.65  13.10                                    AVERAGE    11.71    14.68     11.66  13.28                                    STANDARD DEV.                                                                             0.12     0.75      0.17   0.29                                    ______________________________________                                    

FIG. 10 shows a graph illustrating the statistical distribution of thegenerally uniform cross-sectional diameters found in the thermallyformed suture tip depicted in FIG. 9 and exemplified by Table I above.As shown in FIG. 10, the suture tip produced by the heating dies of thepresent invention has a generally uniform cross-sectional diameter whichcenters about the heating die cross-section (in this case D_(sd2)), andwhich is less than the D_(avg) value corresponding to the unfinishedsuture material 110 supplied to station 400 and forming the untippedbody portion of the resulting suture.

Since the heating die cross-section used in the present invention variesdepending upon the D_(avg) value of the unfinished suture material 110being supplied to machine 10, the heating dies 402, 404 are secured toheater manifolds 410, 412, respectively, by removable screws 414, whichallow an operator to change the heating dies 402, 404 being used instation 400 depending on the size of the suture material 110 being used.A thermocouple 415 for heating the removable heating dies 402, 404 ispositioned in each of the manifolds 410, 412 and coupled to controller800. Thus, for larger diameter suture material 110, the operator willuse heating dies 402, 404 which form a greater heating die cross-sectionthan dies used for thermally forming tips on smaller diameter suturematerial. Set forth in Table IV below are the preferred heating diecross-section diameters used for thermally forming tips on differentsizes of an unfinished braided suture material formed of a polyethyleneterephthalate, such as that sold by Ethicon, Inc. under the trademarkETHIBOND® EXCEL®. Also set forth in Table IV below are the preferredtemperatures that heating dies 402, 404 should be maintained at duringthe heat tipping process, the preferred tensions at which the suturesshould be maintained during the heat tipping process, and the preferreddwell times during which the heating dies 402, 404 should remain closedon the unfinished suture material 110 during the heat tipping process.

                  TABLE IV                                                        ______________________________________                                        SIZE                                                                          OF UN-                                                                        FINISHED                                                                      SUTURE                                                                        MATERIAL                                                                              0        210      3/0    4/0    5/0                                   ______________________________________                                        Heating Die                                                                           17.70    15.00    11.40  9.0    6.85                                  Cross-                                                                        Section                                                                       Diameter                                                                      (in mils)                                                                     Heating Die                                                                           246-250  246-250  246-250                                                                              246-250                                                                              246-250                               Temperature                                                                   (in ° C.)                                                              Heating Die                                                                           2.6-3.0  2.6-3.0  2.6-3.0                                                                              2.4-2.8                                                                              2.0-2.4                               Dwell Time                                                                    (in seconds)                                                                  Tension 100-120  100-120  100-120                                                                              40-60  40-60                                 (in grams)                                                                    ______________________________________                                    

In the preferred embodiment of the present invention, heating dies 402,404 are made of steel, and are coated with a non-stick substance such asTEFLON® (polytetrafluoroethylene polymer) NEDOX®, manufactured byGeneral Magnaplate, in order to facilitate the release of the suturematerial from the grooves 403, 405 when the heating dies 402, 404 areopened. Although in the preferred embodiment described above, theheating die cross-section formed by grooves 403, 405 was circular inshape, it will be understood by those skilled in the art that heatingdie cross-sections defining other geometric shapes may also be used inconjunction with the present invention.

Operation of Cutting Dies

After the cylinders 406 and 408 open the heating dies 402, 404 bybringing them back to their initial retracted positions, therebyexposing a predetermined length of thermally formed surgical suture tipmaterial suspended between opposing open heating dies 402, 404, thecutting dies 450, 452 in the combined heating and cutting station 400operate to cut the thermally formed length of surgical suture tipmaterial. When the present invention is used to create finished suturematerial for "double-armed" sutures (ie., sutures having needles at bothends of each suture), the thermally formed length of surgical suture tipmaterial is preferably cut at its midpoint; otherwise the thermallyformed length of surgical suture tip material is preferably cut near oneof its ends. During the initial operation of the cutting dies 450, 452,the surgical suture material suspended in station 400 remains in thesame position that it occupied during the thermal tipping processdescribed above. Thus, the surgical suture material remains positionedand aligned along axis "x". In addition, during the initial operation ofthe cutting dies 450, 452, the surgical suture material suspended withinstation 400 is maintained at the same present tension that was usedduring the thermal tipping process described above.

FIGS. 11-13 show three further views of the combined heating and cuttingstation 400. Each of the views illustrates the position of the cuttingdies 450, 452 and the cutting blade 480 at a particular point during asuture cutting cycle. During the thermal tipping cycle described above,both of the cutting dies 450, 452 remained in their open or retractedpositions. Following the opening of heating dies 402, 404 at the end ofthe thermal tipping cycle, a mechanical actuator such as a mastercylinder 460 (controlled by controller 800) drives the cutting die 450from its retracted to its extended position. FIG. 11 shows the positionof the cutting dies 450, 452 after the master cylinder 460 has movedcutting die 450 to its extended position. As the cutting die 450 ismoved to its extended position, a cross-section of the thermally tippedsuture material 110a suspended within station 400 is received into agroove or channel 451 (shown in FIGS. 15-16) within cutting die 450. Ameans for positioning and aligning the suture may be used such as a pairof V-shaped guides. A pair of V-shaped guides (not shown) may be affixedto the ends of the cutting die 450 in order to facilitate the guidanceof the thermally tipped suture material 110a into groove 451 during thisstep. In a preferred embodiment of the present invention, the mastercylinder 460 causes the groove 451 in the cutting die 450 to slightlyovershoot the location of the thermally tipped suture material 110asuspended within the station 400, in order to ensure that the entiretyof a cross-sectional portion of the thermally tipped suture material110a is in fact received into the groove 451 (as shown in FIG. 17).

After the master cylinder 460 has moved the cutting die 450 to itsextended position, a mechanical actuator such as a slave cylinder 462(also controlled by controller 800) drives the cutting die 452 from itsretracted to its extended position. FIG. 12 shows the position of thecutting dies 450, 452 after the slave cylinder 462 has moved cutting die452 to its extended position. After the slave cylinder 462 has drivencutting die 452 to its extended position, the face 451a of cutting die450 stands adjacent to and abuts the face 453a of cutting die 452. Thecutting die 452 includes a square-shaped notch (or boss) 453 which isreceived into groove 451 when faces 451a and 453a are brought together.In a preferred embodiment of the present invention, the force used byslave cylinder 462 to drive cutting die 452 to its extended position isless than the force used by master cylinder 460 to drive cutting die 450to its extended position. The use of a reduced force by the slavecylinder 462 insures that the position of the cutting die 450 will notbe disturbed when the cutting die 452 is brought into contact with thecutting die 450 as shown in FIG. 12. After faces 451a and 453a have beenbrought together and the cutting dies 450, 452 have "closed on" thethermally tipped suture material 110a as shown in FIG. 17, blade 480 ismoved by slave cylinder 462 across the thermally tipped suture material110a in a direction perpendicular to the axis "x", thereby shearing thethermally tipped suture material 110a material 110a at a point adjacentto the cutting dies 450, 452 and creating a finished suture 120 having abody portion formed of unfinished surgical suture material 110 and athermally formed tip portion terminating with a cut end. FIG. 13illustrates the positions of the cutting dies 450, 452 as the cuttingblade 480 slices through the thermally tipped suture material 110a, andFIG. 14 shows the proximity of the cutting blade 480 to the cutting dies450, 452 which is maintained during the cutting process. Following theslicing of the thermally tipped suture material 110a, cylinders 460 and462 open the cutting dies 450, 452 by bringing them back to theirinitial retracted positions. As mentioned above, prior to the opening ofthe cutting dies 450, 452 at the end of the cutting cycle, the movingclamp 500 grasps or closes on the surgical suture material 110 at homeposition 510, in order to prevent the tensioning assembly 200 frompulling the trailing end 110b of the surgical suture material cut byblade 480 in a reverse direction past home position 510 when the cuttingdies 450, 452 are opened.

In the preferred embodiment of the present invention, the cross-sectionsof groove 451 and notch 453 are such that, when faces 451a and 453a arebrought into contact with each other as shown in FIG. 17, groove 451 andnotch 453 together form a singular cutting die opening aligned along the"x" axis with a cross-section (hereinafter "the cutting diecross-section") running perpendicular to the "x" axis. Thus, the axis ofthe cutting die opening formed by groove 450 and notch 452 is aligned inparallel with the length of the thermally tipped surgical suturematerial 110a along the "x" axis. In the preferred embodiment of thepresent invention, the diameter "d" (shown in FIG. 17) of the cuttingdie cross-section is always less than the diameter of the heating diecross-section used for thermally forming the tipped suture material110a. By making the diameter of the cutting die cross-section less thanthe diameter of the heating die cross-section, the present inventioninsures that groove 451 and notch 453 not only contact, but also firmlyhold or pinch the thermally tipped suture material 110a positionedbetween the cutting dies 450, 452 during the suture cutting process. Byfirmly holding or pinching the thermally tipped suture material 110a ata point directly adjacent to the location where blade 480 slices throughthe suture material 110a, the cutting mechanism of the present inventionyields a suture with an extremely precise cut end which, among otherthings, facilitates the later insertion of the cut end into a needle.

Alternative Preferred Cutting Die Mechanism

The cutting die system described above in conjunction with FIGS. 11-17is advantageous for creating single-armed sutures which have a needleattached at only one end. However, for some surgical procedures,double-armed sutures which have a needle attached at each end arerequired. In order to manufacture suture material that can be used formaking double-armed sutures, it is important for both ends of the suturematerial to be formed from precise cuts, so that each end of the suturecan be inserted into a needle. An alternative cutting die system 900shown in FIGS. 18-19 may be used in place of the cutting die systemshown in FIGS. 11-17 for fabricating finished sutures 120 having precisecuts at both ends.

System 900 functions substantially the same as the cutting systemdescribed in the section immediately above, except that, in system 900,the master cylinder 460 simultaneously drives a pair of cutting dies902, 904 (respectively the first and second cutting dies) between theirretracted and extended positions, the slave cylinder 462 simultaneouslydrives a pair of cutting dies 906, 908 (respectively the third andfourth cutting dies) between their retracted and extended positions, andthe slave cylinder simultaneously moves two cutting blades 910, 912(respectively the first and the second cutting blades) across twoseparate cross-sections of the thermally tipped suture material 110a.Thus, cutting dies 902, 904 are each substantially identical to cuttingdie 450, and cutting dies 906, 908 are each substantially identical tocutting die 452. During operation of system 900, the master cylinder 460first simultaneously drives the cutting dies 902, 904 from theirretracted to their extended positions. As the cutting dies 902, 904 aremoved to their extended positions, a separate cross-section of thethermally tipped suture material 110a suspended within station 400 isreceived into a groove 451 within each of the cutting dies 902, 904.Next, the slave cylinder 462 simultaneously drives the cutting dies 906,908 from their retracted to their extended positions. After the slavecylinder 462 has driven the cutting dies 906, 908 to their extendedpositions, the faces 451a of the cutting dies 902, 904 stand adjacent toand abut the faces 453a of cutting dies 902, 904. After both sets offaces 451a and 453a have been brought together and the cutting dies 902,904, 906 and 908 have "closed on" their respective cross-sections ofthermally tipped suture material 110a, blades 910, 912 aresimultaneously moved by slave cylinder 462 across two cross-sections ofthe thermally tipped suture material 110a in a direction perpendicularto the axis "x", thereby shearing the thermally tipped suture material110a at two points adjacent to the cutting dies 906, 908 and creatingtwo precisely cut suture ends. Following the slicing of the suturematerial 110a, cylinders 460 and 462 open the cutting dies 902, 904, 906and 908 by bringing them back to their initial retracted positions.

Optical Sensor Control System

The open or closed state/position of the moving clamp 500, thestationary clamp 600, the heating dies 402, 404, and the cutting dies450, 452, as well as the movement and position of the master cylinders406, 460, the slave cylinders 408, 462, the linear actuator 550, thecutting blade 480, and the tensioning assembly 200, are monitored andcontrolled by a controller 800. FIG. 20 shows the positions of severaloptical sensors which are coupled to controller 800, and which monitorand verify the positions of the heating dies 402, 404 and cutting dies450, 452 during the operation of the combined heating and cuttingstation 400. More specifically, optical sensors 801 and 802 are providedfor monitoring/verifying whether heating die 404 is in its extended orretracted position; optical sensors 803 and 804 are provided formonitoring/verifying whether heating die 402 is in its extended orretracted position; optical sensor 805 is provided formonitoring/verifying whether cutting die 450 is in its extended orretracted position; and optical sensor 806 is provided formonitoring/verifyng whether cutting die 452 is in its extended orretracted position. In the preferred embodiment of the presentinvention, controller 800 will not allow the master cylinder 406 todrive the heating die 404 to its extended position unless the sensors805, 806 indicate that the cutting dies 450, 452 are in their retractedpositions; controller 800 will not allow the slave cylinder 408 to drivethe heating die 402 to its extended position unless the sensors 805, 806indicate that the cutting dies 450, 452 are in their retracted positionsand the sensors 801, 802 indicate that the heating die 404 is in itsextended position; controller 800 will not allow the cylinder 460 todrive the cutting die 450 to its extended position unless the sensors801, 802, 803 and 804 indicate that the heating dies 402, 404 are intheir retracted positions; and controller 800 will not allow thecylinder 462 to drive the cutting die 452 to its extended positionunless the sensors 801, 802, 803, 804 and 805 indicate that the heatingdies 402, 404 are in their retracted positions and that the cutting die450 is in its extended position.

FIGS. 21 and 22 show the position of an optical sensor 807 which iscoupled to controller 800, and which monitors and verifies the state(either open or closed) of moving clamp 500. FIGS. 23 and 24 show theposition of an optical sensor 808 which is coupled to controller 800,and which monitors and verifies the state (either open or closed) ofstationary clamp 600.

Suture Tensioning System

Referring now to FIG. 25, there is shown an isometric view of the system200 for tensioning a length of surgical suture material 110, inaccordance with a preferred embodiment of the present invention. System200 includes a tensioning spool 202 having a width, a weight and acircular perimeter 204 perpendicular to the width of the spool. Thetensioning spool 202 has a groove 206 in its perimeter 204 for receivingthe surgical suture material 110. Tensioning system 200 also includes atrack 208 formed from a pair of slots 208a, 208b extending in parallelalong the length of the track 208. Track 208 and slots 208a, 208b arepreferably positioned along a purely vertical axis, although, inalternate embodiments (not shown), track 208 and slots 208a, 208b may bealigned along an axis that includes both horizontal and verticalcomponents. The slots 208a, 208b function to receive and guide thetensioning spool 202 along the length of track 208 during operation ofsystem 200. The length of the track 208 is preferably alignedperpendicularly to the width of the tensioning spool 202.

During operation of the system 200, the tensioning spool 202 issuspended vertically within slots 208a, 208b by the surgical suturematerial 110. While the tensioning spool 202 is suspended verticallywithin slots 208a, 208b by the surgical suture material 110, the weightof the tensioning spool 202 exerts a corresponding tensioning force onthe suture material 110 equal to one half the weight of spool 202. Inorder to vary the tension exerted on the suture material 110 duringoperation of system 200, additional weights 210 may be added or removedfrom a spool arm extending from the center of spool 202.

When the moving clamp 500 described above is in its grasping state andmoves from its home position 510 to its end position 512, suturematerial 110 suspended in the track 208 is drawn forwardly throughstation 400 and stationary clamp 600 of machine 10. As the suturematerial is drawn forwardly through the machine by the moving clamp 500,the tensioning spool 202 is pulled upwardly within track 208. However,regardless of the vertical position of the spool 202 within the track208, the tension exerted on the suture material 110 by system 200 willbe the constant and equal to one half the weight of spool 202. Anoptical sensor 212, coupled to controller 800, is provided fordetermining whether the pulling action of the moving clamp 500 hascaused the spool 202 to be drawn upwardly within the track 208 past theheight of the sensor 212. When optical sensor 212 detects that thetensioning spool 202 has been pulled upwardly past the location of thesensor 212, controller 800 causes a motor (not shown) coupled to thesupply spool 100 to unwind unfinished surgical suture material 110 fromthe supply spool 100. As further unfinished surgical suture material 110is unwound from the supply spool 100, the tensioning spool 202 movesdownwardly within the track 208. In the preferred embodiment, controller800 continues to unwind unfinished surgical suture material 110 from thesupply spool 100 until the tensioning spool 202 falls below the level ofoptical sensor 212.

An optical sensor 214 is provided at the bottom of track 208 fordetermining whether there has been a break in the surgical suturematerial 110 or a loss of tension in the suture material within machine10. Since, during normal operation, the tensioning spool 202 should notfall below the level of optical sensor 212, a break in suture material110 or a loss of suture tension within machine 10 will be signaled bysensor 214 if the sensor determines that the tensioning spool 202 hasfallen to the level of the sensor 214.

Although tensioning system 200 has been described in connection with thetensioning of surgical suture material, it will be understood by thoseskilled in the art that tensioning system 200 may be used for tensioningany type of string or yarn.

Knot Detection System

Referring now to FIGS. 26 and 27, there are shown two isometric views ofan optical detection system 300 for detecting knots in surgical suturematerial 110 passing through system 300, in accordance with a preferredembodiment of the present invention. Knot detector system 300 includesan optical light source 302 for directing a plane of light 304 at anoptical light detector 306 when surgical suture material 110 ispositioned between the optical light source 302 and the optical lightdetector 306 (shown in FIG. 28). The optical light source 302 ispreferably formed of a plurality of optical fibers 302a having theirterminating ends aligned along the optical plane 304. Controller 800 iscoupled to an output of the optical light detector 306 for processingthe signals output by detector 306 and determining whether a knot existsin the suture material 110 positioned between the light source 302 andlight detector 306. More particularly, by comparing a magnitude of ashadow 308 cast on the optical light detector 306 by the suture material110 against a predetermined threshold, controller 800 determines whetheror not a knot exists in the suture material 110 positioned between thelight source 302 and light detector 306. In a preferred embodiment, thepredetermined threshold used in this comparison corresponds to amagnitude of a shadow 308a cast on the optical light detector 306 by anunknoted cross-section of suture material 110. In a still furtherpreferred embodiment, controller 800 will determine that a knot existsin the suture material 110 passing through system 300 only if themagnitude of the shadow cast on light detector 306 by suture material110 exceeds by at least 30% the magnitude of a shadow 308a cast on theoptical light detector 306 by an unknoted cross-section of suturematerial 110.

Although knot detection system 300 has been described in connection withthe detection of knots in surgical suture material, it will beunderstood by those skilled in the art that knot detection system 300may be used for detecting knots in any type of string or yarn.

Extended Length Suture Mode

Although, in the process described above, machine 10 was used tomanufacture a finished surgical suture 120 having a length that was lessthan length of the linear actuator 550, machine 10 may also be used inan extended length suture mode, described below, in order to makefinished surgical sutures which are longer than linear actuator 550. Asshown in FIG. 1, and also in FIGS. 29-31, a suture material holding arm700 affixed to machine 10 is provided for holding suture material duringthe manufacture of extended length surgical sutures. Suture materialholding arm 700 includes an end portion 704 formed of a cylindricalcentral portion bounded by sides 702, 703. An actuator 705, coupled tocontroller 800, drives the end portion 704 between its retractedposition (shown in FIGS. 29-30) and its extended position (shown in FIG.31). When machine 10 functions in its extended length suture mode,actuator 705 maintains end portion 704 in its extended position;otherwise, actuator 705 maintains end portion 704 in its retractedposition.

During operation of the machine 10 in the extended length suture mode,the moving clamp 500 initially grasps or closes on the unfinishedsurgical suture material 110 at the home position 510. Next, while themoving clamp 500 remains in its grasping or closed state, the linearactuator 550 drives the moving clamp 500 from its home position 510 tothe end position 512. As the linear actuator 550 drives moving clamp 500from its home position 510 to its position 512, the moving clamp 500pulls a length of the unfinished surgical suture material 110 throughthe combined heating and cutting station 400 and through the stationaryclamp 600. After the moving clamp reaches its end position 512, thestationary clamp 600 grasps or closes on the unfinished surgical suturematerial 110 positioned within the stationary clamp 600. The movingclamp 500 then releases the unfinished surgical suture material 110 inits grasp, allowing the suture material 110 previously grasped by themoving clamp 500 to fall onto and be held by the end portion 704. Next,while the moving clamp is in its open or non-grasping state, the linearactuator 550 drives the moving clamp 500 from its end position 512 toits home position 510, where the moving clamp 500 again grasps or closeson the unfinished surgical suture material 110 at the home position 510.After the moving clamp 500 grasps the unfinished surgical suturematerial 110 at the home position 510 for the second time, thestationary clamp 600 opens. Thereafter, while the moving clamp 500remains in its grasping or closed state and the stationary clamp 600remains in its open state, the linear actuator 550 again drives themoving clamp 500 from its home position 510 to the end position 512.After the moving clamp 500 reaches its end position 512 for the secondtime, the stationary clamp 600 again grasps or closes on the unfinishedsurgical suture material 110 positioned within the stationary clamp 600.

After the unfinished surgical suture material 110 has been "pulledtwice" by the moving clamp 500 as described in the paragraph above, theheating dies 402, 404 and the cutting dies 450, 452 in the combinedheating and cutting station 400 function as described above to thermallyform and cut a length of surgical suture tip material positioned withinthe station. After the cutting dies 450, 452 move from their closedposition to their open position following the cutting of the suture tip,the stationary clamp 600 releases the surgical suture material withinits grasp. As the stationary clamp opens and releases the previouslygrasped surgical suture material, a finished surgical suture 120 havinga thermally formed and cut tip falls by gravity onto an arm affixed tothe stationary clamp 600. Since the moving clamp 500 pulled the suturematerial 110 two times consecutively before the combined heating andcutting station 400 thermally formed and cut the suture tip, theresulting finished surgical suture 120 produced by the extended lengthsuture mode may have a length which is greater than the length of thelinear actuator 550.

Furthermore, it is to be understood that although the present inventionhas been described with reference to a preferred embodiment, variousmodifications, known to those skilled in the art, may be made to thestructures and process steps presented herein without departing from theinvention as recited in the several claims appended hereto.

What is claimed is:
 1. A method for forming a cut end of a surgicalsuture tip having a length and a cross-section that is perpendicular tosaid length, comprising the steps of:(A) positioning said length of saidsurgical suture tip at a position between a channel in a first face of afirst cutting die and a second face of a second cutting die, saidchannel being aligned along a common axis; (B) after said positioningstep, receiving at least a portion of said cross-section at a locationalong said length of said surgical suture tip into said channel andmoving said first and second faces of said first and second cuttingdies, respectively, against each other, said channel and said secondface defining a singular cutting die opening when said first face ofsaid first cutting die is positioned against said second face of saidsecond cutting die, said singular cutting die opening having across-section perpendicular to said common axis that is small enough tocompress said cross-section of said surgical suture tip when said firstface of said first cutting die is positioned against said second face ofsaid second cutting die; and (C) forming said cut end by moving acutting blade across a point adjacent to said location when said firstface of said first cutting die is positioned against said second face ofsaid second cutting die.
 2. The method of claim 1, wherein said secondface of said second cutting die includes a notch extending therefrom,said channel in said first face being sized to receive said notch whensaid first and second faces of said first and second cutting dies,respectively, are moved against each other in step (B);wherein saidchannel and said notch are brought into contact with an outer surface ofsaid cross-section of said surgical suture tip when said first andsecond faces of said first and second cutting dies, respectively, aremoved against each other in step (B), said channel and said notchdefining said singular cutting die opening when said first face of saidfirst cutting die is positioned against said second face of said secondcutting die.
 3. The method of claim 2, wherein said channel in saidfirst face of said first cutting die is sized to receive all of saidcross-section of said surgical suture tip at said location along saidlength.
 4. The method of claim 3, wherein said cross-section of saidsurgical suture tip is circular.
 5. The method of claim 4, wherein saidchannel in said first face has a cross-section that is semi-circular inshape.
 6. The method of claim 5, wherein said notch has a rectangularshape.
 7. The method of claim 1, wherein step (A) further comprises thestep of aligning said length of said surgical suture tip along saidcommon axis.
 8. The method of claim 7, further comprising the stepof:(D) after said forming step (C), moving said first cutting die fromits extended position to its retracted position, and moving said secondcutting die from its extended to its retracted position.
 9. The methodof claim 8, wherein step (B) further comprises moving, with a mastercylinder coupled to said first cutting die, said first cutting die fromits retracted to its extended position with a first force, and moving,with a slave cylinder coupled to said second cutting die, said secondcutting die from its retracted to its extended position with a secondforce that is smaller than said first force.
 10. The method of claim 9,wherein said first face of said first cutting die includes a V-shapedgroove for directing said cross-section of said surgical suture tip intosaid channel in said first face of said first cutting die as said mastercylinder moves said first cutting die from its retracted to its extendedposition.
 11. The method of claim 10, wherein said master cylindercauses said channel in said first face to overshoot said cuttingposition of said surgical suture tip as said master cylinder moves saidfirst cutting die from its retracted to its extended position in step(B).